A utility grid may provide electric energy to consumers, wherein the electric energy is supplied via an energy stream or a power stream having a predetermined frequency, such as 50 Hz or 60 Hz. While consumers extract electric energy from the utility grid, electric power production units or electric power production plants supply electric energy into the utility grid. If a balance between extracted energy and supplied energy is disturbed, the grid frequency will change. Thereby, in order to maintain the frequency of the utility grid at the predetermined grid frequency, there the extracted energy and the supplied energy must balance.
In particular, when more energy or more power is extracted from the utility grid than power is supplied to the utility grid, the frequency of the utility grid drops. Thereby, problems occur regarding operation of electrical devices which are supplied with electric energy from the utility grid. In particular, these electrical devices may not operate properly or may even be damaged by the supplied electric energy not having the predetermined grid frequency.